App Crashing on Bot Error

[llegoelkelo]

Relates to #1156

I find my app crashing whenever the bot throws. Is there a way to prevent this from happening?

[vaagnavanesyan]

@llegoelkelo you can handle all unhandled Promise rejections (not only from this library) by adding listener for unhandledRejection events.

The easiest way is to add following code before await this.app.listen(port);:

process.on('unhandledRejection', (reason) => {
      console.error(reason);
    });

If you prefer more robust way (e.g. sending logs or any other action in case of error) you can achieve that by two following steps:

1. Declare class-wrapper for unhandledRejection handler:

import { Injectable, Logger } from '@nestjs/common';

@Injectable()
export class UnhandledLogger {
  private readonly logger: Logger = new Logger(UnhandledLogger.name);
  constructor() {
    process.on('unhandledRejection', (reason) => {
      this.logger.error(reason);
      // here you can do anything else
    });
  }
}

2. Add that wrapper to AppModule providers array:

providers: [
    UnhandledLogger,
    {
      provide: APP_GUARD,
      useClass: AuthenticationGuard,
    },
  ],

Second approach is more flexible because UnhandledLogger is simple NestJS Service so you can use IoC, DB connections and anything else.

To test this solution you can simply run two instances of your NestJS application.